This invention relates generally to seal-less integral-motor fluid pumps and more particularly to an improved diaphragm for physically isolating the motor stator from the motor rotor and the pumped fluid.
A seal-less pump which has the motor rotor integrated into the impeller and the stationary windings of the stator isolated from the pumped fluid requires a diaphragm to accomplish such isolation of the stator. The diaphragm must be non-metallic in most designs to minimize eddy current losses and to permit efficient electromagnetic coupling of the rotor and stator. Since the pumped fluid may be a corrosive or otherwise dangerous chemical, and since the diaphragm is exposed to the pump discharge pressure, the diaphragm must be constrained to prevent rupture or blow-out. Diaphragms are commonly clamped between housing members of the pump, and, non-metallics being of low elastic modulus, are subject to distortion due to creep induced by the constant high clamping force. The diaphragm is weakened by the reduction of thickness, and it ultimately fails. Such failures can be very costly, since the applications for seal-less pumps are usually for handling dangerous and chemically aggressive fluids.
The foregoing illustrates limitations known to exist in present diaphragms in seal-less integral motor pumps, and it would be advantageous to provide an alternative directed to overcoming one or more of those limitations. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.